The present invention relates to bridging conveyors used with packaging apparatus. In particular, it relates to such bridging conveyors which can be retracted from the conveying plane at times during the packaging process and which can be driven.
Often, modern day packaging machinery is designed to process an assortment of sizes, shapes and weights of product. This versatility is particularly true with newer computer controlled machinery. Packaging machinery systems usually have a sealing head area where product which had been previously wrapped can be sealed, or where product is wrapped and sealed. The sealing head area machinery is fed product by an input conveyor and wrapped product is carried away by a discharge or output conveyor.
Typically, the input and discharge conveyors are spaced from the sealing head area machinery necessitating the use of bridging conveyors therebetween. This spacing is desirable to allow access to the sealing head area machinery for changeover, maintenance and cleaning without the removal of the input and discharge conveyors. While access to the space about the seal head area machinery requires removal of the bridging conveyors, this involves much less time and work than removal of input and discharge conveyors.
Stease, U.S. Pat. No. 3,944,037, shows a retractable bridging conveyor which is stored on a large drum and can be reeled out to a desired length like a garden hose. Stease's bridging conveyor uses a separate support structure to hold his flexible multi-link side rails. The conveyor has driven rollers suspended between the multi-link side rails. These rollers are driven by driving the home or feed drum end of the roller structure and thereafter coupling each successive roller along the conveyor length with idler gears, the rollers thereby being serially, drive-connected. This link rail, roller, and idler gear structure leaves a significant gap between the bridging conveyor and a mating feed conveyor.
Suga, U.S. Pat. No. 4,144,697, shows two separate bridging conveyors. The first is an endless chain belt conveyor positioned between a supply convey and the sealing head area. A separate side engagement drive structure moves product along this first bridging conveyor.
The second Suga bridging conveyor connects his sealing head area to a discharge conveyor. This second conveyor, which is an endless chain roller conveyor, also operates as the product support medium through a wrapper folding area. The rollers of this second conveyor are spaced sufficiently apart to allow wrapper film to drop therebetween under the affects of a vacuum created below through a vacuum licensing. Unlike Stease, neither the first nor the second Suga, '697, bridging conveyors are retractable.
Suga, U.S. Pat. No. 4,841,715, shows a first bridging conveyor connecting a vacuum actuated film sweeping area to a discharge conveyor. This first bridging conveyor is a continuous chain roller conveyor of sprocket drive design.
Suga, '715, also shows a vacuum actuated film sweeping work station having a short product carrying conveyor which connects or bridges between the output of a film cutting station and the first bridging conveyor. This second bridging conveyor is also of a continuous chain roller conveyor of sprocket drive design. However, it has a short rollerless section which defines a single large gap in the roller belt assembly thereby providing a large opening for drawing film therethrough under the force of a vacuum from below. This second bridging conveyor is a modification of the second bridging conveyor shown previously by Suga in the '697 patent.
Michels, U.S. Pat. No. 4,180,962, shows an automatic wrapping machine which utilizes a chain roller film sweeping device. This film sweeping device is implemented by chain roller assembly of sprocket drive design. However, contrary to the Suga, '715, conveyor, Michels has a short roller section while the larger portion of his assembly is rollerless.
The Michels', '962, device is suspended above the line of product flow. It operates to move the short roller section thereof to bridge a space between a supply conveyor and a movable roller carriage, thereby intercepting and sweeping wrapping film to a position under the product. In this operation, the short roller section of the device displaces the roller carriage which is normally positioned to abut the discharge end of the supply conveyor.
Once film is swept, other large overhead drive rollers move the product off of the roller assembly. Thereafter, the roller assembly is retracted by movement in the opposite direction.
While the Michels' roller section does in fact support product, it does not cause nor impart motion to the product.
These prior art structures are supported and driven by chain link mechanisms, or chain roller mechanisms or chain belt mechanisms. These structures have inherent in their design a "give" or "stretch" which, especially at high speeds, contributes to limitations in the accuracy of timing and sequencing of operations. Moreover, as bridging conveyors are intended to be removable, these above-described structures may require the disassembly and reassembly of many parts.
A rotating, bar rider device has been used as a bridging conveyor. This structure includes a single rotatory shaft positioned between two supports and extending transversely across a space between the output plate of a packaging machine sealing head area and a discharge or output conveyor. This device is generally more rugged and capable of more precise drive timing and sequencing operations than the other prior art described above.
The rotating bar rider conveyor includes a curved plate attached to and positioned outwardly from the rotating shaft. This curved plate extends parallel to the longitudinal axis of the shaft for a length equal to the width of the space to be bridged by the bridging conveyor. This curved plate also extends in an arc path about the shaft for a distance from about 60 to 120 degrees. As the shaft rotates, the curved plate rotates. The rotation is timed for the curved plate to intercept a package and to carry it across the space from the sealing head area to the output (discharge) conveyor. In higher speed operations, two diametrically opposed curved plates have been mounted on the shaft.
This rotating, bar rider conveyor device, like the Stease, '037, retractable bridging conveyor, is limited to handling larger packages or product. Smaller packages or product tend to fall and/or become trapped in the space between the discharge edge of the sealing head area apparatus and the beginning of the bar rider bridging conveyor curved plate, which operates as the product support surface.
Therefore, it is desirable to provide a simple, rugged and accurately timed bridging conveyor which is easily disassembled and reassembled. This bridging conveyor needs to fill the entire space from the discharge edge of the sealing head area apparatus to the adjacent end of an output (discharge) conveyor and thereby eliminate any small spaces where small packages can fall and/or become trapped. It is further desirable that this bridging conveyor impart motion to a product or package which enters onto the bridging conveyor.